New Push to Make Paying Full Price for a Hotel Room Passé

When Craig Foster needed a place to stay for a March trip to San Diego, the best rate he could find for the Bahia Resort Hotel was $147 a night. Then one website he tried, Stayful.com, said it would bid $130 a night for him.

Sure enough, the hotel immediately offered him the room at the reduced rate. That amounted to a savings of just over $100 for his six-night stay. "It seemed a bit too good to be true," Mr. Foster, an...